Estimation of Gene Effects in Four Bivoltine Silkworm (Bombyx mori L.) Crosses

Abstract

Six generations (P1, P2, F1, BC1, BC2 and F2) of four bivoltine silkworm crosses (SKAU-R-1 ´ Yakwei, SKAU-R-6 ´ Yakwei, CSR2 ´ CSR4 and SH6 ´ NB4D2) were evaluated in a completely randomized block design with 5 replications for each treatment. The generation mean 2 in respect of 3 metric traits (single cocoon weight, single shell weight, and shell ratio %), were subjected to Cavallis joint scaling test. Additive dominance model was found to be adequate in CSR2 ´ CSR4 and SH6 ´ NB4D2 for single cocoon weight and shell weight and SKAU-R-6 ´ Yakwei for shell ratio (%). Whereas, in rest of the crosses epistasis was evident in the traits under investigation. Magnitude of additive gene effect (d) was greater than dominance (h) in SH6 ´ NB4D2 and SKUA-R-6 ´ Yakwei for shell ratio (%) and in CSR2 ´ CSR4 for shell weight. Thus selection for these traits in early segregating generations of these crosses would be effective for obtaining considerable genetic gain.